Production and use of a urea suspension



Jan. 17, 1956 s. THORNES PRODUCTION AND USE OF A UREA SUSPENSION IN OIL Filed May 16, 1951 NW 952 5. ww N zohuliz QN QN Leslie Senior Thornes Attorneys United States Paten PRODUCTION AND USE A UREA SUSPENSION This invention relates to an improved process for the production ofurea in finely divided form and to the refining of petroleum by meansof urea in finely divided form... i

It is Well-known that ureaforms crystalline solid adducts with straight chain and slightly branched chain hydrocarbons but does not form solidcomponnds with naphthenes, highly branc hed compounds oraromatics. By the use of urea a. method has ,beendeveloped for refining petroleum fractions by resolution ofthe fractions into by formingthe above solid compounds, separating the non-solid residue and subsequently, decomposing the solid compounds. 3

It; is also known that the urea .adducts may be decomposed by the action of heat alone with separation of a hydrocarbon phase and a liquid urea phase.

The use of the recovered urea. for the production of further amounts of urea-adductsis complicated by the difiiculty of returning the urea in a form suitable for the formation of the adductsat a satisfactory reaction rate.

It is an object of the present inventionto provide a process for the production ofa urea-containing agent foruseinthe formation of urea adducts. It is a further object to produce: urea in the form of a urea-in-oil suspension. It is a still further object, to provide an improved process for the production of urea adducts using urea-inoil'suspensions. It is a still further object to provide a process for the refining of petroleum using urea-in-oil suspensions.

According to the present invention a urea-containing.

agent is produced for use in the formation of urea adducts, by a .process which comprises contacting urea with a hydrocarbon oil at elevated temperature, preferably 132- 14( C., forming an emulsion of the liquid urea in the oil andshock cooling the emulsion to form a urea suspension in oil by a rapid addition of a hydrocarbon oil at a tem: perature below that of the emulsion and in an amount suflicient to solidify the urea Preferably the hydrocarbon oil is an oil which is to be treated with urea to form urea adducts. The preferred hydrocarbon oils are fractions of petroleum. Preferably urea, in the liquid phase, is contacted with oil at a temperature above 132 C. and preferably in the range 132 C9140 C. i i i Byoperating in the above manner, the urea is converted to small 'crystals suspended in the oil phase which are readily convertible to ureaadductson subjecting the suspension to adduct forming conditions. Urea recycle when operating in the manner described may closely approach 100%.

Under preferred operation theurea crystals in suspension constitutte 50-100% by weight of the hydrocarbon oil employed.

According to a further embodiment of the present invention hydrocarbon oils having a low content of normal paraflins and slightly branched paraifins are produced by a process which comprises treating a petroleum material chemical types 2,731,457 Patented Jan. 17, 1956 selected from the group comprising crude petroleum, stabilised petroleum anddistillation fractions of petroleum with a urea-in-oil suspension under conditions such that a solid urea adduct is formed, separating a liquid urea adduction raffinate phase comprising naphthenes, highly branched chain hydrocarbons and aromatics from the, said product, decomposing the adduct: by heat in the absence ofwater, separating the urea so formed from the ,1

urea adduction extract comprising straight chain andslightly branched chain hydrocarbons, contacting the urea with a hydrocarbon oil at elevated temperature, forming an emulsion of liquid urea in the oil and shock cooling the emulsion to form a urea suspension in oil by a rapid addition of a hydrocarbon oil at a temperature below that of the emulsion and in an amountsuificient to solidify the urea, and recycling the urea-in-oil suspension for further reaction with further amounts of the petroleum material.

Preefrably the reaction of urea is carried out in the presence of an alkanol of low molecular weight, suitably The preethanol and propanol. i

According to a further embodiment of the'present in-. vention, hydrocarbon oils are produced by treating a liquid petroleum fraction with a urea-in-oil suspension,

an alkanol of low molecular weight and a hydrocarbon diluent, under conditions such that a product comprising.

a solid urea adduct is formed, separating a liquid phase comprising a hydrocarbonoil from the said product,

decomposing the adduct by heat in the absence of water,

separating urea and converting it to a urea-in-oil suspendescribed, returning the urea-in-oil suspension to the treating stage and recovering said liquid sion as hereinbefore phase, with or without removal of the hydrocarbon dilu- .ent contained therein.

Preferably the hydrocarbon dilueut is a petroleum fraction, substantially free of compounds forming urea adducts under the conditions of theprocess, and boilingbelow the boiling range of the petroleum fraction undergoing treatment. Using a hydrocarbon diluent of this type, the

urea adduct, on decomposition by heat, forms a hydro carbon-methanol phase which may be subjected to fractional distillation whereby a mixture of methanol and hydrocarbon diluent is removed overhead and a normal parafiin containing fraction of the initial feedstock is recovered as bottoms. The overhead fraction of this fractional distillation is then recycled to the urea adduct forming stage.

According to one manner of operation of the process,

for the produciton of fuel suitable for use in gas turbine engines, the hydrocarbon diluent selected is a suitable component for the finished fuel. The liquid phase obtained on separation of the urea adduct from the ureainactive components is a mixture of branched chain hydromarbons, naphthenes, aromatics and the hydrocarbon ,diluent and is suitable for use asa fuel without separation ,of the diluent.

According to this aspect of the invention, crude petroleum or stabilised crude petroleum or the distillation frac- .tion derived from petroleum is fractionally distilled for urea adduction feedstock are derived from a common source, the 'feedstockto a preliminary distillation stage for the separation of diluent and urea adduction feedstock may be a petroleum fraction boiling in the range 100 C.-350 C. Conveniently the diluent and urea adduction feedstocks may be obtained as straight run side streams in the distillation of crude petroleum;

Urea adductionis carried'out at a temperature in the range 20- C.40 C. and, quite conveniently, in therange 20 C.-25 C.

The proportions-of reactants in the urea adduction stage depend on the n-paraflin contentof the feedstock and the degree of removal of n-parafiins which is desired. It has been shown that approximatelyone mole of urea is re quired for each CHz-group in the n-parafiin. Thus for complete removal of n-parafiins (taken as CI3H28) from a gas oil of 200" to 350"C. boiling range containing 15- per cent by weightofn-paraflin, approximately" 0.5 lb. of urea per lb. of gas oil feedstock will be required. The proportion of recycle oil in the adduction stage will depend on the proportion of reactants and the consistency of the resulting adduct stream. Using 0.5 lb. of urea per lb. ofgas oil, a recycle oil ratio of 1.76 gallons of recycle oil per gallon of gas oil is, in general, satisfactory.

The presentinvention is illustrated but in no way limited with reference to the figure accompanying" the specification which is a flow diagram of a process for the production of a gas turbinefuel wherein urea is recycled to the adduct forming reactor in the manner hereinbef'ore described...

The reactor l'fitted with astirrer 2 receives make-up quantitiesof urea by line 3 and a mixture of feedstock, urea,- hydrocarbon diluent, methanol feed oil and recycled oilgby line 4. The slurry formed in the reactor passes by line-5 to a rotary filter 6 which is sprayed'with' further quantities of hydrocarbon diluent from line 7; Wet adduct. cake. is. removed by line- 8 to decompose!" 9; The product from. decomposer 9 passes to separator 10 in which. a hydrocarbon-methanol phase is removed'by line- 11, through heater 12 to fractionator 13- in which a normal parathn containing fraction isremoved as bottomsthrough line; 1.43 and. cooler 15. A mixture of methanol and hydrocanbondiluent is removed overheadi fromfractionator 13 by line.1.6", through cooler'1'7 and line 18 and is recycled to the reactor; 1 by line. 4: A mixture of urea-inactive components of: the feedstock together with hydrocarbon diluent is removed. from filter 6' by lines-19 and constitutes-:- thefinishedfuei; Liquidurea; is removed from the sepa-- ratorglo tby 1ine:20;an,d-is. passed to an. emulsifier 21 fed with hot-.fcedzoil. by line: 222from heater 28. The emulsified-rurea/oil mixture; is removed by line.- 23. and is: shock cooledtby admixture-withireslroih feed from line- 24 and recycled finished fuel from line 25. The mixture passes through. cooler 26 and-line 27' for recycle to thereactor 1. Make-up methanol passes; by? line: 29. to: line 4.

A. suitable feedroil. to. ther-processis: a straight. run: gas oilboiling, in the;range.'200. to. 35.0.? A. suitable hydro-- carbon diluent is: a; kerosine. fraction boiling; in. the. range 100. to 20.0" C.

In. place of. urea there may: be; employed; substituted: urea, for example; alkyli substituted" ureas.

I claim:

1... A. process for the: production: of: a1 men-containing ageutionuse imthe.formatiomohureazadducts; which com-- prises contacting urea. with hydrocarbon. oilv atsel'evated temperature; forming an;emulsiorr'ofi liquid urea in. the oil,and.shock.cooling,the; emulsionto; formna urea suspentemperature below that of the emulsion and in an amount sufficient to solidify the urea.

'2. A process for the production of a urea-containing agent for use in the formation of urea adducts, which comprises contacting urea with a distillation fraction of petroleum at elevated temperature, forming. an emulsion I of liquid urea in the oil and shock cooling the emulsion to form a urea suspension in oil by a rapid addition of a hydrocarbon oil at a temperature below that of the emulsion and in an amount sufiicient to solidify the urea.

3. A process for the production of a urea containing agent for use in the formation of urea. adducts,.which comprises contacting urea with a hydrocarbon oil at elevated temperature, forming an emulsion of liquid" urea in the oil and shockcooling the emulsionto form a urea suspension in oil by a rapid addition of a distillation fraction of petroleum at a temperature below that of the emulsion and in an amount sufficient to solidify'the urea;

4. A process for the production of a urea containing agent for use in the formation of urea adducts, which comprises contacting urea with a distillation fraction of petroleum at elevated temperature, forming an emulsion. of liquid urea in: the oil and shock cooling" the emulsion to form a urea suspension in oil by a rapid addition of a further quantity of the said distillation fraction at atem-- perature below that of the emulsion and" in an amount sufficientto'solidifytheurea:

5. A process as specified in claim 4' in'whichthe: dis

tillation fractionis-employed inan amount such that the urea suspension in oil contains 5010.0% by weight of" urea,. based on the amount of hydrocarbon oil-contained therein;

6. A process as specified in claim 5 in whichthehydro carbon oilwith which the urea is contacted i's'at a temperature in the range 1'3'2-140 C. and in which the urea is contacted while in the liquid phase with the said' oil.

7. A process for the production of hydrocarbon oil's which-comprises treating a petroleum material selected from the group comprising crude. petroleunn. stabilised crude petroleum and distillation fractions of petroleum with a urea-in-oil suspension under conditions such that a solid urea adduct is formed, separating a liquid urea adductionraflinatephase comprisinghighlybranched chaini hydrocarbons, naphthenes and aromatics from the said product, decomposingthe-adduct= by'heat in the-absence'of water,.separating the urea so formed from the urea adduction extract= comprising straight chain and slightly branched chainhydrocarbons; contacting the urea with" a hydrocarbon oil at elevated temperature, forming an' emulsion of li'quid urea in the oil" and shock cooling the emulsion to forms ureasuspension inoil byfa rapid addition" of a hydrocarbonoil ata temperature below that offthe emulsion and in an amountsufli'cient' to solidify-the urea and recycling the urea-i'n-oil suspension for furtherremc tion with further amounts of the-petroleum material References Gitedin the: file-of: this patent.

UNITED. ST ATES' PATENTS 

